Marathons have never been more popular, as statistics somewhere probably show. This is very good news for people who like to watch marathons, and for businesses that sell Band-Aids and Vaseline, and for whoever holds the patent for the Mylar space blanket.

If you actually run marathons, however, well, heaven help you. Journalists are falling over each other to report on the risks you take when you run 26.2 miles. That's not to mention the common knowledge that you're ruining your knees, which is an obvious true fact, as your non-running friends, relatives, coworkers, and total strangers will tell you. Honestly, you might as well save yourself the entry fee and just stand around pounding your kneecaps with a pair of ball-peen hammers for three or four hours.

But if you thought that's where the risks ended, you're wrong. A "deeper dive" into the medical literature reveals several more, lesser-known hazards of running marathons, each more awful than the last. For instance...

1. Ice Cream Headache

Researchers at UC San Diego made a startling discovery when they surveyed finishers of the 2011 San Diego Rock 'n' Roll Marathon: Their subjects were twice as susceptible to "brain freeze," a.k.a. ice cream headache. Doctors are at a loss to explain it, but in the meantime they urge marathoners to avoid ice cream cones and milkshakes. The risks just aren't worth it.

2. Rake Accidents

Among healthy adults who report having stepped on a rake carelessly left lying on their lawn, resulting in a comical but painful smack in the face, a full 30% ran a marathon in the 8 weeks prior to their accident.

3. Paralyzing Sense of Existential Dread

Multiple studies have found a link between finishing a marathon and experiencing a sudden, overwhelming fear that life is nothing but a brief and meaningless march from birth to death and that, in the end, we are alone in a cold and absurd universe. The onset often occurs while uploading data to an online training log.

4. "Oh, Come On!" Moments

In a little-noticed 2009 study, researchers at the University of Florida found that marathon runners saw a spike in "Oh, Come On!" moments in the weeks before and after race day. Such moments included: locking their keys in the car, waiting 15 minutes for their bagel to toast before realizing that the toaster was unplugged, realizing that they totally forgot to put the trash out on trash night, and locking their keys in the car again.

5. Spider Eggs in Ears

A small study of lifelong runners in Germany recently found that those who ran marathons were 15% more likely than a control group to have a spider crawl into their ears as they slept, lay eggs, then have the eggs hatch weeks later and feel baby spiders skittter out of their ears.